GLUCOCORTICOID RECEPTORS IN LEUKOCYTES AND GILL OF JUVENILE COHO SALMON (ONCORHYNCHUS-KISUTCH)

We demonstrated that cytosol from the gill of coho salmon (Oncorhynchas kisatch) had saturable, high affinity, low capacity binding to radiolabeled [3H]cortisol (Kd = 2.24 ± 0.28 nM, mean ± 1 SE; Nmax = 41.4 ± 7.4 fmol/mg protein) and radiolabeled [3H]triamcinolone acetonide (TA; Kd = 0.38 ± 0.03 nM, Nmax = 37.8 ± 4.9 fmol/mg protein). Similarly, TA bound to cytosolic fractions of leukocytes harvested from spleen (Kd = 0.32 ± 0.03 nM, Nmax = 8.3 ± 2.0 fmol/mg protein) and anterior kidney (Kd = 0.37 ± 0.03 nM, Nmax = 30.2 ± 5.2 fmol/mg protein) and to whole leukocytes from spleen (Kd = 0.30 ± 0.04 nM, Nmax = 445 ± 57 sites/cell) and anterior kidney (Kd = 0.40 ± 0.04 nM, Nmax = 1198 ± 180 sites/cell). The competition hierarchies of steroid competitors were the same for both ligands and all tissues (TA > cortisol > 17α-hydroxyprogesterone > cortisone > aldosterone > testosterone). The differences in ligand binding in leukocytes from spleen and anterior kidney are consistent with previously reported organ-dependent sensitivity of leukocytes to cortisol. © 1990.